1. Field of the Invention
The present invention relates to golf clubs called wood clubs or woods, and more particularly to golf clubs having an improved relation between the axis of the club shaft and the hitting spot on the club face.
2. Description of the Prior Art
In case of the wood clubs among the conventional golf clubs, an axis X passing through the center of the shaft 1 thereof and a line X' passing through the hitting spot H and parallel to the axis X lie in a plane squarely facing to the golfer as shown in FIG. 1. Assume here that the distance between X and X' in the above-mentioned plane is y. The hitting spot H on the club face lies before the axis X in the direction of ball's flight. Taking as positive the relation between the axis X and hitting spot H when the former is before the latter and the relation as negative when the former is after the latter, the distance y between X and X' is within a range of about -5 to -20 mm with the woods, and is within a range of about -1 to 5 mm with the irons.
Conventionally, the heads 2 of woods are made of a persimmon. For the persimmon-made heads, the value of y has to be set to less than -15 mm for reasons of their strength. The heads of woods have been traditionally made of a persimmon. The shape of the wood-club head made of persimmon has been taken even in case the club heaads are made of a metal or FRP (fiber reinforced plastic). As the result, the woods have the head shape rather different from the shape of the irons.
Currently, the heads 2 of woods are made of a metal, FRP or the like and have a considerably high strengh as compared with the persimmon head, but remain almost unchanged in shape. That is to say, any of the club heads 2 made of persimmon, metal and FRP, respectively, has a shape with the value of y being less than -5 mm, so that hitting of the ball B by an average golfer with a wood is likely to result in a slice. He swings trying to hit the ball B at a spot of the club head which lies on the shaft 1, namely, on or near the extension of the grip. Then the ball B is hit by the club head earlier than he thinks because the hitting spot H lies before the shaft 1. The ball is hit by the club head before he has completely directed the club face toward the target. That is, the ball is hit with the club face open. At this time, a slicing rotation is imparted to the ball as shown in FIG. 3 even if the head 2 is swung along the line of ball' s flight Z. Also at the time of his swing, the wrist rotates (causing the rotation of the head around the shaft 1 and rolling of the head) and the velocity v of the hitting spot H resulting from the wrist rotation acts to impart a slicing rotation to the ball B as shown in FIG. 2. This velocity v of the hitting spot H is determined from the equation v=r .omega. (where r is a distance from the center of the rolling to the hitting spot H and .omega. is an angular velocity of rotation). If he tries to hit the ball B with the club face somewhat closed on purpose as shown in FIG. 4 in order to correct the slice, the ball thus hit will result in a hook. However, this hitting technique cannot easily be attained by average golfers. The professional and skillful golfers have a full understanding of the differences besween the woods and irons and use the clubs based on their skill and extensive experience. The majority of the average or beginner golfers use both the woods and irons in a same manner. The ball hit by the average golfer with a wood is apt to result in a slice.